A relay system is used to increase cell coverage without extending a base station and obtain better system throughput. The relay station (hereinafter, referred to as ‘relay’) is divided into a single hop relay and a multiple hop relay. In view of a mobile station, the relay is divided into a transparent relay and a non-transparent relay. Also, the relay may be divided into a fixed type and a mobile type. In order to support a relay in a system, the corresponding relay should be defined definitely. For this reason, an action type of a relay supported by the system is limited. In order to support a relay system of which standardization does not end, like IEEE 802.16, or support a new relay, a type of a relay supported by the base station should be considerably generic and should not depend on a relay structure.
FIG. 1 is a diagram illustrating a configuration of a system and an interface type when a relay is included in the system.
In FIG. 1, if a mobile station (MS) can directly communicate with a base station (BS), the mobile station performs direct communication. If the mobile station needs assistance from a relay station (RS) due to great path loss, the mobile station transfers a signal through the relay. Also, the mobile station can use multiple relays for diversity or can transfer a signal through the relay while performing direct communication with the base station.
If a single relay joins in a signal transfer procedure from the mobile station to the base station, the relay will be referred to as a single hop relay. If several relays join in the single transfer procedure, the relays will be referred to as multi-hop relays. IEEE 802.16m system requirements prescribe that a system for supporting multi-hop relays should be provided. Since an air interface supporting the IEEE system has not been finally determined, an interface provided by the base station should be considerably generic so as to support a system which is not completed, like IEEE 802.16m.
FIG. 2 is a diagram illustrating a type of a peer-to-peer communication on a protocol stack of a system which is generally used.
If a structure of a relay is defined definitely, a protocol stack can be defined, and definite interface and procedure can be defined for each layer.
However, in a state that an actual operation of the system is not definite, it is not preferable to design interface and procedure for an unknown protocol.